1. Field of the Invention
This invention relates to detergent compositions containing a protease and combinations of proteases in addition to standard surfactants and which are particularly effective in removing stains and combinations of stains from soiled fabrics such as wool without damaging the fabrics.
2. Description of the Related Art
Enzymes, more particularly proteolytic enzymes, are widely used in laundry detergents, washing aids and cleaning compositions. At present, proteases from the subtilisin family are exclusively used. These are extracellular proteins with a molecular weight in the range from about 20,000 to 45,000. Subtilisins are relatively non-specific enzymes which show esterolytic properties in addition to their hydrolytic effect on peptide bonds. Many representatives of the subtilisins are accurately characterized both physically and chemically. Their three-dimensional structure is often known in detail through X-ray structural analysis. This establishes the prerequisites for molecular modeling and so-called protein engineering in the form of controlled mutagenesis. Genetically engineered modifications of proteases have often been described; thus, 219 protein variants of the subtilisins obtained by protein engineering were known as long ago as June, 1991. Most of these variants were produced to improve the stability of the proteases. For example, an active protease from the subtilisin family which is stable under highly alkaline conditions can be produced in Bacillus lentus (DSM 5483), as described in U.S. Pat. No. 5,352,604, the entire contents of which are incorporated herein by reference. This Bacillus lentus alkaline protease (BLAP) can be produced by fermentation of the Bacillus licheniformis which was transformed with an expression plasmid carrying the gene for BLAP under the control of the promoter from Bacillus licheniformis ATCC 53926. Both the composition and the three-dimensional structure of BLAP are known. This protease contains 269 amino acid sequences, a calculated molecular weight of 26,823 Daltons and a theoretical isoelectric point of 9.7. Variants of this Bacillus lentus DSM 5483 protease obtainable by mutation are described in U.S. Pat. No. 5,340,735, the entire contents of which are incorporated herein by reference.
The proteases hitherto proposed for use in detergents and washing aids were selected for high proteolytic activity. On account of their low specificity, therefore, fiber damage or fiber destruction by the protease can occur in particular in the event of repeated washing of fabrics of proteinogenic fibers, for example sheet-form textiles of silk or wool. On the other hand, any reduction in protease activity results in a loss of cleaning power noticeable to the user of the detergent. Accordingly, one problem addressed by the present invention was to develop protease-containing detergents which would show reduced activity on proteinogenic fibers, more particularly wool, for substantially the same washing activity. Another problem addressed by the present invention was to develop soil-specific proteases which are proteases that remove specific stains on fabrics such as eggs stains and blood stains and detergent formulations containing such soil-specific proteases.